DP Chemistry (first assessment 2025)

Question 19M.2.SL.TZ2.3b(ii)

Date	May 2019	Marks available	[Maximum mark: 2]	Reference code	19M.2.SL.TZ2.3b(ii)
Level	SL	Paper	2	Time zone	TZ2
Command term	Calculate	Question number	b(ii)	Adapted from	N/A

b(ii).

[Maximum mark: 2]

19M.2.SL.TZ2.3b(ii)

(b(ii))

A sample of gas was enriched to contain 2 % by mass of ¹⁵N with the remainder being ¹⁴N.

Calculate the relative molecular mass of the resulting N₂O.

[2]

Markscheme

« $\frac{{(98 \times 14) + (2 \times 15)}}{{100}}$ =» 14.02 [✔]

«M_r = (14.02 × 2) + 16.00 =» 44.04 [✔]

Examiners report

Most candidates were able to calculate the accurate mass of N₂O, though quite a few candidates just calculated the mass of N and didn’t apply it to N₂O, losing an accessible mark.

Syllabus sections

Structure 3. Classification of matter » Structure 3.2—Functional groups: Classification of organic compounds » Structure 3.2.8—Mass spectrometry (MS) of organic compounds can cause fragmentation of molecules. Deduce information about the structural features of a compound from specific MS fragmentation patterns.

Question 19M.2.SL.TZ2.3b(ii)

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